National Ambulatory Medical Care Survey: 2005 summary.

Abstract

This report describes ambulatory care visits made to physician offices in the United States. Statistics are presented on selected characteristics of the physician's practice, the patient, and the visit.
The data presented in this report were collected in the 2005 National Ambulatory Medical Care Survey (NAMCS), a national probability sample survey of visits to nonfederal office-based physicians in the United States. Sample data are weighted to produce annual national estimates of doctor visits.
During 2005, an estimated 963.6 million visits were made to physician offices in the United States, an overall rate of 331.0 visits per 100 persons. In one-quarter of office visits, electronic medical records were utilized by physicians, while at 83.9 percent of visits, claims were submitted electronically. As the baby boomer generation aged, there was a shift in utilization, as the majority of visits in 1995 were by patients 25-44 years of age compared with 2005, when most visits were by patients 45-64 years of age. In 2005, 52.7 percent of office visits were made by patients with at least one chronic condition. Hypertension was the most frequent condition (22.8 percent), followed by arthritis (14.3 percent), hyperlipidemia (13.5 percent), and diabetes (9.8 percent). Medication therapy was reported at 679.2 million office visits, accounting for 70.5 percent of all office visits. In 2005, there were about 2.0 billion drugs prescribed, resulting in an overall rate of 210.7 drugs per 100 visits. Drugs with amoxicillin were more likely to be new prescriptions (85.4 percent), while ibuprofen and acetaminophen were just as likely to be a new or continued drug. The overall mean time spent with a physician, excluding psychiatrists, has not changed since 1995; however, visits with a duration of 6-10 minutes decreased by 28% from 1995, while visits lasting 16-30 minutes increased by 20%.

Full text

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Number 328 + June 5, 2002
National Ambulatory Medical Care Survey: 2000 Summary
by Donald K. Cherry and David A. Woodwell, Division of Health Care Statistics
Abstract
Objective—This report describes ambulatory care visits made to physician
offices within the United States. Statistics are presented on selected characteristics
of the physician’s practice, the patient, and the visit. Highlights of trends in
physician office visit utilization from 1997 through 2000 are also presented.
Method—The data presented in this report were collected from the 2000
National Ambulatory Medical Care Survey (NAMCS). NAMCS is part of the
ambulatory care component of the National Health Care Survey that measures
health care utilization across various types of providers. NAMCS is a national
probability sample survey of visits to office-based physicians in the United States.
Sample data are weighted to produce annual national estimates. Trends are based on
NAMCS data from 1997 through 2000.
Results—During 2000, an estimated 823.5 million visits were made to
physician offices in the United States, an overall rate of 300.4 visits per 100
persons. Approximately half of the visits were made to the patient’s primary care
physician. The proportion of office visits where a physician or physician group was
the owner of the practice has steadily increased since 1997 (74.3 percent in 1997
versus 88.1 percent in 2000). Of all visits made to these offices in 2000,
approximately 57 percent listed private insurance as the primary expected source of
payment, and 29 percent were made by patients belonging to a health maintenance
organization. There were an estimated 89.9 million injury-related visits during 2000,
or 32.8 visits per 100 persons. Blood pressure check was the leading diagnostic
screening test (45.3 percent) and males were more likely than females to have no
diagnostic or screening services mentioned. The proportion of visits with at least
one prescription for cardiovascular-renal drugs, hormones, or metabolic/nutrient
drugs has increased since 1997.
Keywords: physician office visits c diagnoses c injury c medications c ICD–9–CM
Introduction
The National Ambulatory Medical
Care Survey (NAMCS), which began in
1973, collects data on the utilization of
ambulatory medical care services
provided by office-based physicians. It
was conducted annually until 1981,
again in 1985, and resumed an annual
schedule in 1989. The NAMCS is
complemented by the National Hospital
Ambulatory Medical Care Survey
(NHAMCS), which was inaugurated in
1992 to expand the scope of data
collection to the medical services
provided by hospital outpatient and
emergency departments. Together,
NAMCS and NHAMCS data provide an
important tool for tracking ambulatory
care utilization in the United States. A
third survey, the National Survey of
Ambulatory Surgery, was conducted
from 1994 through 1996, to focus on
the rapidly increasing use of ambulatory
surgery centers that are not covered in
the NAMCS or the NHAMCS. The
NAMCS and NHAMCS are part of the
National Health Care Survey, which
measures health care utilization across
various types of providers. More
information about the National Health
Care Survey can be found at the
National Center for Health Statistics
(NCHS) Internet address: www.cdc.gov/
nchs/nhcs.htm. More information on the
NHAMCS 2000 annual summaries
(hospital outpatient and emergency
departments) is available (1,2). A
separate report combining NAMCS and
NHAMCS data provides a
comprehensive picture of ambulatory
medical care utilization (3). It shows
that 80 percent of ambulatory care
delivered by non-Federal physicians, as
identified by the NAMCS and
NHAMCS, is provided in office-based
practices. Hospital ambulatory patients
are known to differ from office patients
in certain demographic and medical
characteristics.
This report presents national annual
estimates of physician office visits for

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Advance Data No. 328 + June 5, 2002
2000. Physician practice, patient, and
visit characteristics are described.
Data highlights
+ In 2000, 823.5 million visits were
made to physician offices—about
300.4 visits per 100 persons.
+ There was an increasing trend in the
proportion of office visits where a
physician or physician group was the
owner of the practice (74.3 percent in
1997 to 88.1 percent in 2000).
+ The trend in the proportion of visits
to physician offices owned by a
hospital declined since 1997, from
7.6 percent to 2.7 percent.
+ The visit rate for white persons (3.2
visits per person) was higher than for
black persons (2.1 visits per person).
+ Patients who had seen the physician
before accounted for 86.2 percent of
office visits.
+ Patients were referred from another
physician or health plan at
16.8 percent of visits.
+ Approximately 30 percent of visits
were by members of health
maintenance organizations.
+ Medicare or Medicaid was the
expected source of payment at
28.3 percent of all visits.
+ General medical examination was the
most frequently mentioned reason for
visit, accounting for 7.8 percent of all
office visits.
+ Complementary and alternative
medical therapies were ordered or
provided at 31.6 million physician
office visits, representing 3.8 percent
of all visits.
+ Since 1997, there was an increase in
the percent of office visits where a
cardiovascular-renal drug (by 21%),
hormone (by 25%), or metabolic/
nutrient drug (by 49%) was ordered,
supplied, administered, or continued.
Methods
The data presented in this report are
from the 2000 NAMCS, a national
probability sample survey conducted by
the Division of Health Care Statistics of
NCHS, Centers for Disease Control and
Prevention. The survey was conducted
from December 27, 1999, to December
24, 2000.
The target universe of the NAMCS
includes visits made in the United States
to the offices of nonfederally employed
physicians (excluding those in the
specialties of anesthesiology, radiology,
and pathology) who were classified by
the American Medical Association
(AMA) and the American Osteopathic
Association (AOA) as ‘‘office-based,
patient care.’’ Visits to private,
nonhospital-based clinics and health
maintenance organizations (HMOs) were
within the scope of the survey, but those
that took place in federally operated
facilities and hospital-based outpatient
departments were not. Telephone
contacts and visits made outside the
physician’s office were also excluded.
The NAMCS utilizes a multistage
probability sample design involving
samples of primary sampling units
(PSUs), physician practices within
PSUs, and patient visits within
physician practices. The PSUs are
counties, groups of counties, county
equivalents (such as parishes or
independent cities), or towns and
townships for some PSUs in New
England. A sample of 3,000 physicians
was selected from the master files of the
AMA and the AOA, and 2,049 were in
scope, or eligible to participate in the
survey. Sample physicians were asked to
complete Patient Record forms (see
figure I in the Technical notes) for a
systematic random sample of office
visits occurring during a randomly
assigned 1-week reporting period. The
response rate for in-scope physicians
was 67.7 percent, and a total of 27,369
Patient Record forms were completed.
The Technical notes provide more
information on characteristics of
nonresponding physicians.
Because the estimates presented in
this report are based on a sample rather
than on the entire universe of office
visits, they are subject to sampling
variability. The Technical notes at the
end of this report include an explanation
of the sampling errors with guidelines
for judging the precision of the
estimates and information on physician
and item nonresponse. The standard
errors reported here are calculated using
Taylor approximations in SUDAAN,
which take into account the complex
sample design of the NAMCS (4).
The U.S. Census Bureau was
responsible for data collection. Data
processing operations and medical
coding were performed by Analytical
Sciences, Inc., Durham, North Carolina.
As part of the quality assurance
procedure, a 10-percent quality control
sample of survey records was
independently keyed and coded. Coding
error rates ranged between 0.0 and
1.6 percent for various survey items.
Several of the tables in this report
present data on rates of physician office
visits. The population figures used in
calculating these rates are based on
Census Bureau monthly postcensal
estimates of the civilian noninstitutional
population of the United States as of
July 1, 2000. The figures have been
adjusted for net underenumeration using
the 1990 National Population
Adjustment Matrix.
Data on selected physician office
utilization trends from 1997 through
2000 are also presented. A weighted
least-squares regression analysis was
used to determine the significance of
trends at the 0.05 level. For details on
the surveys conducted from 1997
through 1999, refer to the annual reports
(5–7).
Results
There were an estimated 823.5
million visits to office-based physicians
in 2000, about 300.4 visits per 100
persons. The population-based visit rate
did not change significantly from the
visit rate in 1997. Annual visit rates
ranged between 278.5 and 307.8 visits
per 100 persons between 1997 and 2000
(5–7). Selected characteristics of the
encounter pertaining to the physician’s
practice, the patient, and the visit are
described in the following text.
Physician practice characteristics
The distribution of office visits
according to physician specialty is
presented in table 1. About 60 percent of
the visits were to physicians in the
primary care specialties of general
family practice (GFP), internal
medicine, pediatrics, and obstetrics/
gynecology (figure 1). The visit rates for
each specialty did not differ
significantly from the 1997 visit rates.

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Advance Data No. 328 + June 5, 2002
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Internal medicine
Pediatrics
12.6%
Ob/Gyn
7.9%
Ob/Gyn is obstetrics/gynecology.
1
Ophthalmology
5.2%
Orthopedic surgery
5.6%
All other
29.4%
24.1%
15.2%
1
General and family practice
Figure 1. Percent of office visits by physician specialty: United States, 2000
1997
1998
1999
2000
0
10
20
30
40
50
60
70
80
90
Physician or physician group
Hospital
NOTE: Trends shown are significant (p<0.05).
Percent

of visits

Figure 2. Trends in the percent of physician office visits by practice ownership: United
States 1997–2000
The distribution of visits is similar to
the NAMCS estimated distribution of
practicing physicians in 2000 with
several exceptions. Pediatricians
received 12.6 percent of visits, but
accounted for only 8.7 percent of
physicians, and GFPs represented
17.1 percent of office-based physicians,
but had 24.1 percent of the patient
encounters. Conversely, psychiatrists
comprised 6.5 percent of office-based
physicians, but accounted for only
3.5 percent of the visits.
Table 1 also shows that doctors of
osteopathy received 66.7 million visits
during 2000, or 8.1 percent of all office
visits. Visits to these types of doctors
occurred at a rate of 24.3 visits per 100
persons. Visits according to geographic
region and metropolitan status of the
physician’s practice are also displayed
in table 1. The visit rate for the
Northeast region (350.6 visits per 100
persons) was significantly higher than
the rate in the South (259.3 visits per
100 persons).
Additional information on the
physician’s practice has been collected
annually in the NAMCS through the
Physician Induction Interview (PII)
form. The PII is used to obtain basic
information on the practice, establish the
visit sampling rate, and record the final
disposition of the interview. In 2000,
selected survey items on the physician
and physician’s practice, including
employment status, ownership, practice
size, and office type, were edited and
weighted to produce national estimates
of office visits by these characteristics.
These data are displayed in table 2. The
majority of office visits (62.8 percent)
were made to physicians engaged in
group practice, while 37 percent of the
visits were to solo practitioners. The
proportion of office visits where a
physician or physician group was the
owner of the practice has steadily
increased since 1997. Figure 2 shows an
increasing trend in this proportion along
with a decrease in the percent of visits
where the physician office was owned
by a hospital (7.6 percent in 1997 versus
2.7 percent in 2000).
Patient characteristics
Office visits by patient’s age, sex,
and race are shown in table 3. Females

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Advance Data No. 328 + June 5, 2002
made the majority of office visits during
2000. Both the visit percent as well as
the visit rate for female patients were
higher than for male patients in the age
groups between 15 and 64 years. As age
increased, the number of patient visits to
office-based physicians rose. There was
a positive linear relationship between
patient age and the number of visits per
100 persons for both male and female
patients. Comparisons of office-based
utilization rates by patient’s age and sex
can be seen in figure 3.
White persons represented
82 percent of the U.S. civilian
noninstitutional population in 2000, but
made 86.3 percent of all physician office
visits. The visit rate for white persons
was 48 percent higher than for black
persons (316.1 versus 213.8 visits per
100 persons, respectively). It should be
noted that visit rates by race vary by
type of health care setting. Data
presented in the 2000 NHAMCS
outpatient department summary indicate
that the visit rate for black persons (48.3
visits per 100 persons) was higher than
for white persons (28.0 visits per 100
persons) (1).
Visit characteristics
Referral status and prior-visit
status—Table 4 shows data on office
visits categorized by patient’s referral
status and prior-visit status. Overall,
patients who had seen the physician on
a prior occasion, ‘‘old patients,’’
accounted for 86.2 percent of the office
visits. Patients that were referred for this
visit by another physician or health plan
accounted for 16.8 percent of the office
visits.
More referrals were made to
specialty physicians (35.0 percent) than
to primary care physicians (4.6 percent)
(data not shown). Table 5 shows this
contrast in more detail. The percent of
referral visits to obstetricians/
gynecologists was low (4.2 and
8.2 percent, for new and old patients). In
contrast, referrals to other types of
specialties were generally much higher.
For example, among neurologists,
25.6 percent of ‘‘new’’ visits and
30.9 percent of ‘‘old’’ visits were
referrals from another physician or
health plan. For the specialty care
providers (not including the specialties
of GFP, internal medicine, pediatrics, or
obstetrics/gynecology), the percent of
visits that were referrals ranged from
23.4 percent to 56.2 percent (data not
shown).
Managed care—Managed care
variables measured in the 2000 NAMCS
are displayed in table 6. These include
whether the visit was made to the
patient’s primary care physician,
All ages Under 15
15 24
25 44
45 64
65 74
75 and
over
0
100
200
300
400
500
600
700
Patient's age in years
Number

of visits

per

100

persons

Female
Male
Figure 3. Annual rate of visits to office-based physicians by patient’s age and sex:
United States: 2000
whether authorization was required for
the visit, whether the visit was capitated,
and whether the patient belonged to a
health maintenance organization (HMO).
Physicians reported that for about
one-half of all office-based visits they
were the patient’s primary care
physician. For this distinction, ‘‘primary
care’’ was not limited to a certain
specialty, as stated earlier in the text,
but was defined by the physician.
Authorization was required to see the
physician at 12.0 percent of office-based
visits overall; however, authorization
was more likely to be required in cases
where the physician reported not being
the patient’s primary care physician
(20.6 percent versus 5.1 percent).
Capitated visits accounted for
10.7 percent of all office-based visits in
2000. Visits where the patient saw his or
her primary care physician were more
likely to be capitated compared with
visits where the patient saw a physician
other than his or her primary physician
(15.4 percent versus 6.2 percent).
Primary expected source of payment
and health maintenance organization
status—The distribution of office visits
by the primary expected source of
payment is shown in table 7. Private
insurance was cited most frequently
(56.7 percent of visits). Government
sources combined (Medicare and
Medicaid) covered 28.3 percent of office
visits, most of which were Medicare.
Except for self-pay, which decreased
slightly, the distribution of expected pay
sources in 2000 did not differ
significantly from the 1997 distribution.
HMO members made close to
30 percent of all office visits. However,
HMO membership varied by expected
source of payment. Thirty-nine percent
of private insurance visits were HMO
enrollees, in contrast to 11.8 percent and
20.1 percent for Medicare and Medicaid,
respectively. Figure 4 shows how the
type of payment varies by patient age.
The proportions of visits where private
insurance was the expected source of
payment were similar for patients under
age 18 years (66.2 percent) and for
visits where the age range was 18–64
years (69.9 percent). As expected,
elderly patients (65 years of age and
over) were less likely to utilize private
insurance (18.7 percent) and more likely

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Advance Data No. 328 + June 5, 2002
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All ages
Under 18
18-64
65 and
over
0
20
0
Percent of visits
0
0
100
Patient’s

age

in years

Private
insurance
Medicare
Medicaid
Worker's
compensation
Self-pay
No charge
Other
Unknown/blank
468
Figure 4. Percent distribution of office visits by primary expected source of payment
according to patient’s age: United States, 2000
to use Medicare as the primary source
of payment at physician office visits
(71.0 percent).
Patient’s principal reason for
visit—The principal reason for visit is
the main complaint, symptom, or reason
listed why the patient came to the
physician’s office. Up to three reasons
for visit were coded according to A
Reason for Visit Classification for
Ambulatory Care (RVC) (8). The RVC
is a classification scheme developed by
NCHS and has been used for over 20
years to code patients’ complaints or
reasons for seeking care. It is divided
into eight modules or groups of reasons
as shown in table 8 and includes all the
reasons for which patients see their
physicians. This includes symptoms,
followup for prior diagnoses, routine
examinations and screening, treatment
for conditions and operations, various
therapies, and injuries. Also included are
visits to receive test results and to fulfill
third party requirements for a physical
examination, such as for employment
or a driver’s license. The symptoms
module is further divided into symptoms
that refer to specific body systems, such
as digestive or respiratory. Each reason
is assigned a 3- or 4-digit classification
code (for example, S845– ‘‘Symptoms
of skin mole’’ is further detailed to
S845.1– ‘‘Change in size and color’’ and
S845.2– ‘‘Bleeding mole’’).
In 2000, close to one-half of all
visits were made for reasons classified
as symptoms. Some of the more
prominent symptoms included
musculoskeletal (9.7 percent), respiratory
(9.6 percent), and symptoms referable to
the skin, hair, and nails, which
accounted for 5.8 percent of all visits.
About 18 percent of office visits were
for diagnostic, screening, and preventive
services. The 20 most frequently
mentioned principal reasons for visit,
representing 40.7 percent of all visits,
are shown in table 9. Similar to recent
years, general medical examination was
the most frequently mentioned reason
for visit at 7.8 percent of all office
visits, while cough was the most
frequently mentioned reason regarding
an illness or injury (2.7 percent).
Nineteen of the top 20 reasons for office
visits in 2000 were also listed among
the 20 most frequently mentioned
reasons in 1997, albeit in different order.
It should be noted that estimates that
differ in ranked order may not be
significantly different from each other.
Major reason for this visit—The
intent of this item was to provide a
better picture of the general nature of
the office visit—whether for an acute
problem, routine chronic problem,
flare-up of a chronic problem, pre- or
post-surgery visit or injury followup, or
for preventive care, including routine
medical examinations. The major reason
for visit item differs from the principal
reason for visit item in that the former
presents the physician’s rather than the
patient’s perspective of the major reason
the patient sought care. Overall,
35.0 percent of the visits were for an
acute problem. However, among visits
by persons under 15 years of age,
50.2 percent were for acute problems
(table 10). In general, more than
one-quarter (28.0 percent) of all visits
were for a routine chronic problem and
there was a significant linear trend that
showed an increase in the visit
proportion as a function of patient age.
About 19 percent of all visits were for
preventive or nonillness care, but
females had a higher proportion of visits
for this type of care compared to males.
This reflects, in part, that preventive
care includes prenatal examinations.
Trend data from 1997 through 2000
indicate that the percent of visits
classified as ‘‘acute’’ for patients under
15 years of age decreased from
53.9 percent to 50.2 percent (figure 5).
Primary diagnosis—Physicians
were asked to record the primary
diagnosis or problem associated with the
patient’s most important reason for the
current visit and any other significant
current diagnoses. Up to three diagnoses
were coded according to the ICD–9–CM
(9). Displayed in table 11 are office
visits by primary diagnosis using the
major disease categories specified in the
ICD–9–CM. The supplementary
classification, used for diagnoses that
are not classifiable to injury or illness
(for example, general medical
examination, routine prenatal
examination, and health supervision of
an infant or child), accounted for
18.1 percent of all office visits. Diseases
of the respiratory system (11.0 percent)
and diseases of the nervous system and